 /*******************************************************************************
  * Copyright (c) 2005, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/

 package org.eclipse.ui.internal.menus;

 import org.eclipse.core.expressions.Expression;
 import org.eclipse.ui.ISources;
 import org.eclipse.ui.internal.services.EvaluationResultCache;

 /**
  * <p>
  * A token representing the contribution of a menu element. This token can later
  * be used to cancel that contribution. Without this token, then menu element
  * will only become inactive if the component in which the handler was
  * contributed is destroyed.
  * </p>
  * <p>
  * This caches the menu element, so that they can later be identified.
  * </p>
  * <p>
  * This class is not intended for use outside of the
  * <code>org.eclipse.ui.workbench</code> plug-in.
  * </p>
  *
  * @since 3.2
  */
 final class MenuContribution extends EvaluationResultCache implements
         IMenuContribution {

     /**
      * The menu element that has been contributed. This value may be
      * <code>null</code>.
      */
     private final MenuElement menuElement;

     /**
      * The menu service from which this menu contribution was request. This
      * value is never <code>null</code>.
      */
     private final IMenuService menuService;

     /**
      * Constructs a new instance of <code>MenuContribution</code>.
      *
      * @param menuElement
      * The menu element that has been contributed. This value may be
      * <code>null</code>.
      * @param expression
      * The expression that must evaluate to <code>true</code>
      * before this menu contribution is visible. This value may be
      * <code>null</code> if it is always active.
      * @param menuService
      * The menu service from which the contribution was requested;
      * must not be <code>null</code>.
      * @see ISources
      */
     public MenuContribution(final MenuElement menuElement,
             final Expression expression, final IMenuService menuService) {
         super(expression);

         if (menuElement == null) {
             throw new NullPointerException (
                     "The menu element for a contribution cannot be null"); //$NON-NLS-1$
 }

         if (menuService == null) {
             throw new NullPointerException (
                     "The menu service for a contribution cannot be null"); //$NON-NLS-1$
 }

         this.menuElement = menuElement;
         this.menuService = menuService;
     }

     public final MenuElement getMenuElement() {
         return menuElement;
     }

     public final IMenuService getMenuService() {
         return menuService;
     }

     public final String toString() {
         final StringBuffer buffer = new StringBuffer ();

         buffer.append("MenuContribution(menuElement="); //$NON-NLS-1$
 buffer.append(menuElement);
         buffer.append(",menuService="); //$NON-NLS-1$
 buffer.append(menuService);
         buffer.append(",sourcePriority="); //$NON-NLS-1$
 buffer.append(getSourcePriority());
         buffer.append(')');

         return buffer.toString();
     }
 }

